1. Field of the Invention
The present invention relates to an intake system for a combustion engine, particularly that used in a motorcycle.
2. Description of the Prior Art
As a high power combustion engine for racing motorcycles, the combustion engine has hitherto been well known, in which first and second fuel injectors are employed in each of intake passages leading to respective engine cylinders and are operated simultaneously during a high power operation. The first and second fuel injectors are positioned downstream of a throttle valve in a throttle body and upstream of an suction duct protruding into an air cleaner forming a part of the intake passage, respectively. In this combustion engine, the distance between an injection port of the second fuel injector and a combustion chamber of the engine is set relatively long by positioning the second fuel injector within the air cleaner distant from the combustion chamber. This structural feature is effective to facilitate a fine atomization of fuel being injected into the combustion chamber.
However, with compactization of the motorcycle advanced, the fuel intake passages in the conventional intake system are limited as to their size and shape. In particular, since the second fuel injector is arranged above (upstream of) the suction duct that protrudes into the air cleaner as discussed above, the air intake space above the suction duct is limited, resulting in the intake efficiency being lowered. See, for example, the Japanese Laid-open Patent Publication No. 2004-60552.